Summary of Work: Studies on oncogene activation in spontaneous and chemically induced rodent neoplasms started several years ago in collaboration with molecular biologists at NIEHS have been largely completed. Samples were obtained from both the National Toxicology Program bioassays and from rodent studies designed to investigate the pathogenesis of neoplasia and strain susceptibility to genotoxic and nongenotoxic agents. Current work has been expanded to investigate the role of suppressor genes and growth factors in carcinogenesis to identify susceptibility factors that impact on carcinogenesis. During the past year efforts have been directed toward developing a PCR procedure to identify Helicobacter hepaticus in mouse livers to determine the effect of the spontaneous infection on development of liver tumors. This project will be completed in September 1997.